Process for treating petroleum oils



Patented Dec. 18, 1928.

UNITED STATES PATENT OFFICE.

WALTER M. CROSS, OF KANSAS CITY, MISSOURI, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO GASOLINE PRODUCTS" COMPANY, INC., 0]? WILMINGTON, DELAWARE, A. COR- PORATION OF DELAWARE PROCESS FOR TREATING PETROLEUM OILS.

Application filed October 14, 1922. Serial No. 594,493.

This invention relates to improvements in a process for treating petroleum oils, and refers more particularly to a process in which oil is first raised to a conversion temperature in a heating zone and thence passed to a conversion zone wherein the oil is maintained in a substantial body, the pressure bein bullt up by evolved gases and maintaine sufliciently high to prevent any substantial vaporization of the oil during the heating and conversion thereof.

Among further objects of the invention are to provide a process in which the oil, after being'permitted to digest in the converslon chamber wherein the molecular rearrangement takes place whereby lighter hydrocarbons are contained in the oil in a state in which they may be readily separated therefrom by simple distillation, is passed to a separate distilling stage and there relieved of these light hydrocarbons under either atmospheric or superatmospheric pressure; to provide a process in which certain cuts of the distilled product may be re-run through the system to produce further conversion, and a process which consists of a primary and secondary stage, the cracking taking place in the primary stage wherein a synthetic product is formed and a secondary stage in which this synthetic product is relieved of its lighter ends, and in general to provide an apparatus for carrying out this process.

Fig. 1 is a diagrammatic side elevational view of the apparatus with parts in section.

Fig. 2 is a top view of the conversion chambers showing the alternate meansfor cutting out the separate chambers for cleaning. Referring to the drawings, the oil to be treated is introduced from any convenient source through the line 1, controlled by a valve 2, passed through the line 3 to a pump 4 by means of which it-is charged through the line 5, controlled b a valve 6, to the up-- per coil 7 situated in the top compartment 8 of the furnace 9. The oil is circulated downwardly through this coil to the bottom tube of the upper coil 7 from which it passes into a transfer line 10 which is connected with the lower tube of the coil 11 mounted in the lower compartment of the furnace 9. In this lower compartment the oil receives the greater part of its heating and passes from the upper tube of the coil 11 through a transfer line 13 controlled by a valve 14 to the insulated conversion chamber 15 which is equipped with a pressure gauge 16 and a pyrometer 17. The oil is permitted to collect in a substantial body in the chamber 15 and is maintained both in the heating coils and conversion chamber at sufficient pressure to prevent any substantial vaporization. The pressure maintained is due to the evolution of gases.

At the opposite end of the conversion chamber is a draw off line 18, controlled by a valve 19 which connects the chamber with an adjoining still 20 which is mounted above a furnace 21 preferably heated by means of gas burner 22. The amount of oil drawn off through the line 18 serves to regulate the speed of flow of oil through the conversion chamber. This flow is regulated to permit the oil to have ample time to digest or assume an equilibrium in the reacting chamber. This digestion consists primarily in a rearrangement of the molecules of the oil into a synthetic product which consists in a larger percent of lower boiling point hydrocarbons. To promote this reaction on the bottom of the chamber 15 is positioned a perforated pipe 21 which is controlled by a valve 22*. Through the perforations in this pipe may be introduced a combustion supporting gas or gases such as air or oxygen in regulated quantities which serves to regulate the temperature of the reacting oil in the chamber. It is only essential that the oil in the heating tubes be heated to a. temperature above its flash point. Then by the introduction of a combustion supporting gas in the reacting chamber the temperature of conversion may be accurately controlled and preferably maintained above that of the oil in the heating tubes. This reduction of temperature in the heating tubes greatly reduces the collection and accummulation of carbon in the hotter portions of the heating tubes thereby permitting the apparatus to be run over a considerably longer period of time than has heretofore been the practice, due to the necessity of cleaning the carbon from the heating tubes.

Furthermore, the introduction of a combustlon supporting gas to the conversion chambers serves to keep the oil in a turbulent and agitated condition thereby keeping any carbon particles which will separate out during the digestion period in .a suspended state, and will reduce materially the accumulation of free carbon inthe conversion chamber. Thus the synthetic product discharged into the still will contain this carbon in a suspended state and after distillation the residual substance consisting of the unvaporized oil and this carbonaceous matter, may be drawn ofl from the still through the line 23 in which isinterposed the valve 24.

. It is understood, of course, that these conversion chambers may be connected with one or more stills so that the oil removedfrom the reacting chamber may be immediately subjected to distillation to remove the lighter hydrocarbons.

A further advantage of this type of apparatus is the fact that there is very little heat lost in the system as the synthetic product is immediately introduced to a distillation process into which it is passed at a temperature suflicient to produce immediate vaporization with the reduction of pressure which takes place on its passing through the reduction valve 19.

In Fig. 2 are shown alternate chambers 25 and 26 which may be used in place of the single reacting stage 15. In case the alternate chambers of the type shown are used the transfer line 13 will be connected to a header 27 having secondary connections 28 and 29 to the respective chambers. In a like manner the draw off line 18, will have to be connected into a header 30 which is equipped with connections 31 and 32 tapped into the respective chambers. It is essential also that valves 28, 29, 31 and 32 be interposed in the respective connections, in order to control the flow of liquids to cut out one chamber and cut in the other while one is being cleaned. It is understood also that Separate perforated pipes will necessarily be positioned on the bottom of each of the alternate chambers if such an installation is desired.

With the reduction of pressureon the oil as it is introduced into the still there will immediately be a considerable evolution of vapors and gases and under certain conditions it will be practically. unnecessary to supply any substantial amount of heat by means of the furnace 21. With certain oils, however, it will be necessary to add heat to the oil in the still. The operation of this still will be governed to a great extent by the character of the oil used and also the quality of distillate which is desired. At any event there will be a substantial reduc tion of pressure from the reacting stage and conditions in the still will range from atmospheric to pressures considerably above atmos heric pressure.

The vapors evolved in the still pass off through the line 33 which is controlled by the throttle valve 34 and are introduced to the lower header of a reflux condensing element- 35. This element and the adjoining condenser 36 are identical in form consisting of an upper and lower header with connecting tubes through which the vapors pass and are subjected to the cooling effect of the atmosphere. The vapors rising through the tubes in the reflux condenser separate outa liquid product which passes down through the condenser coil 37 situated in the condenser box 38.- The discharge end of the coil terminates in the line 39 regulated by a valve 40 which is connected to a storage tank 41.- The uncondensed vapors pass off from the upper header of the reflux condenser 35 through the line 42 regulated by a valve 43 and are charged to the lower header of the .reflux condenser 36. Herein the vapors are subjected to a secondary dephlegmation or reflux condensation. The liquid separated out in this reflux condenser flows down through the coil 44 also mounted in the condenser box 38. This coil is likewise connected by a line 45 regulated by a valve 46 to the tank 41. Those vapors which remain uncondensed after passing through the element 36 are directed ofl throu h the line 47 in which is interposed a va ve 48 and after passing through the condensing coil 49 are drawn off-through the line 50 in which is interposed a valve 51 to a benzine storage tank not shown. The liquids collected by reflux condensation in the reflux condensers 35 and 36 are combined and collected as explained in the tank 41 from which they would be drawn off through the line 52 controlled by a valve 53, or they may be directed back through the line 3, re ulated by a valve 54, and charged with t e incoming charging stock to the pump 4 for recirculation through the system.

As explained'this system is particularly adapted to the conversion or cracking of charging stock such as gas oil, kerosene distillates, fuel oil, or other types of oils which can be commercially treated under pressure 1m to remove lowboiling point products. The oil is circulated through the heating coils in the manner describedv and therein is raised to temperatures ranging from 600 to 900 F.

It is then-passed to the digestion or reacting chamber where higher temperatures, as from 700 to 900 F., are preferably maintained. The introduction of a combustion supporting gas facilitates the control of temperature in this stage. The oil from the conversion stage is passed to the still 20 wherein there is a substantial reduction of pressure which is controlled by the valve 19. In the still under normal operation substantially 90% of theoil passes overhead in the form of vapors while 10% bottoms are removed through the residual draw off line. The vapors are conducted through the reflux condensing stages and separate cuts made, the final product being collected in 0 a storage tank while the reflux condensates may be collected and re-run or drawn oil? as desired.

The pressures operated on in the heating and reacting chambers preferably range from 400 to 750 pounds. These pressures are adapted to maintain such products as have a critical temperature below the temperature of the oil in substantially a liquid phase.

I claim:

1. A process for treating petroleum oil consisting in raising the oil to a conversion temperature in a heatin stage, passing the oil to a reacting stage an maintaining a pressure from 400 to 750 pounds per square inch upon the heating and reacting stages, introducing a combustion supporting gas to the reacting stage to raise the temperature therein in excess of the temperature in the heating stage, pasing the converted product from the reacting stage to a distillation stage maintained under reduced pressure, refluxing the evolved vapors in separate stages of dephlegmation and collecting the separated products.

2. A process for treating petroleum oils consisting in raising the oil to a conversion temperature in a heating stage, passing the heated oil to a reacting stage and maintaining a pressure from 400 to 750 pounds per square inch upon the heating and reacting stages, injecting a combustion supporting gas to the oil body in the reacting stage for maintaining the temperature therein above that obtaining in the heating stage, passing the converted product from the reacting stage to a distillation stage maintained under reduced pressure, refluxing by successive stages of dephlegmation the vapors evolved in the distillation stage, collecting and returning selected portions of these reflux condensates for retreatment in the heating stage, and removing selected portions from the system.

3. A process for heating petroleum oil consisting in raising the oil above its flash point in a heating stage, passing the heated oil to a digestion stage and there maintaining it in a substantial body under a pressure from 400 to 750 pounds per square inch, injecting a combustion supporting gaseous material to the digestion stage for maintaining a predetermined temperature in the digestion stage and above the temperature in the heat ing stage during the period of reaction,

passing the digested product to a distillation stage maintained under reduced pressure consisting in raising the oil at least to its flash point in a heating stage, passing the oil to a reacting stage and maintaining a pressure from 400 to 750 pounds per square inch upon the heating and reacting stages, introducing a combustion supporting gas in regulated quantities to the lower portion of the oil body maintained in the reacting stage whereby a predetermined conversion temperature is maintained by a partial combustion'etfected in the chamber whereby the temperature of the oil in the reaction stage is raised and maintained above that in the heating stage, passing'the converted products to a stage of reduced pressure and distilling off the lighter fractions with the contained heat of the oil, refluxing the evolved vapors and subjecting the lighter fractions to a final condensing action.

5. A process for treating petroleum oils, consisting in raising the oil at least to its flash point in a heating stage, passing the oil to a reacting stage and maintaininga pressure from 400 to 750 pounds per square inch upon the heating and reacting stages, introducing a combustion supporting gas in regulated quantities to the oil body maintained in the reacting stage whereby a predetermined conversion temperature is maintained by a partial combustion effected in the chamber whereby the temperature of the oil therein is raised above that in the heating stage, passing the converted products to a stage of reduced pressure and distilling off the lighter fractions with the contained heat of the oil, and adding sufiicient heat to obtain the vaporization of the relaively less volatile fractions, subjecting the evolved vapors to a action, collecting and returning said refiilxed condensate to the heating stage for retreatment, and separately condensing the gasoline-like fractions and collecting them as distillate.

WALTER M. CROSS. 

